Problem: Last Monday, Christopher's parents gave birth to twins and named them Emily and Tiffany. When they were first born, Emily weighed 8.19 pounds and was 20.5 inches tall, and Tiffany weighed 8.94 pounds and was 18.5 inches tall. How much did the babies weigh in total?
Answer: To find the weights of the 2 babies, we need to add their weights together. Emily's weight + Tiffany's weight = total weight. ${8}$ ${1}$ ${9}$ ${8}$ ${9}$ ${4}$ ${+\vphantom{0}}$ ${3}$ ${1}$ ${7}$ ${1}$ Together, the babies weigh 17.13 pounds.